It is well known that a large number of higher melting particulates can be used as nucleating agents in highly crystalline polymers of propylene and other crystallizable thermoplastic polymers. As disclosed in U.S. Pat. No. 3,367,926, a wide variety of higher melting compounds will function as nucleating agents if present as small particles in the molten polymer as it solidifies upon cooling.
Many practical advantages can accrue from the proper use of effective nucleating agents in crystallizable thermoplastics. For example, as shown in U.S. Pat. No. 3,852,237, superior clarity or translucency characterizes films and articles formed from such polymer melts containing fine particulate nucleating agents in low concentrations of of from 0.001 to 0.5% by weight.
However, in commercial practice, it is difficult to achieve a completely uniform dispersion of the nucleating agent throughout the bulky mass of base polymer. In fact, it has generally been necessary to use high energy, intensive mixing equipment in order to avoid visible specks in the finished product and to use unduly prolonged mixing cycles in order to assure a uniform concentration of the finely dispersed nucleator throughout the entire base polymer in commercial scale operations.